This is the process I used to test my collection of Type 3 Oil Coolers:

I used my tap to clean up the boss threads:

I used a small 10mm x 1.00mm pitch plug to plug the boss. You can find this plug in your pile of parts left from taking some solex carburetors apart:

I used a dab (end of a q-tip amount) of Gasoila on the threads, along with a used 10mm sealing washer.

I gathered up the bolts and washers need to attached the pressure testing plate:

Attached the testing plate:

A bit of liquid dishwashing type soap where the schrader valves contact the aluminum to help that interface seal.

The Blue Bentley indicates a test pressure of 85psi. I figured 60psi was good enough. So pressured up the unit and set it down underwater in the sink. Swished it around to get any trapped air out of the fins. After several minutes with no evidence of air streaming from the unit, I felt it was good:

Installation:
From the FAQ regarding Oil Seals; I know what the correct combination answer is. But, I'll go through 4 different scenarios to demonstrate.

The Blue Bentley, the Brown Bentley, the Haynes, and the Clymer manuals can all lead you down a bad installation path if you are not aware of the details in the Oil Seal FAQ and what is shown below. All of these manuals make a point that you should install the oil cooler Spacer Rings and the Deflector Plate.

I have a later model case (U50304920) that has 10mm oil passages in the case, with a 58 fin, 10mm oil passage oil cooler. From the Oil Seal FAQ we know that I should use the thin red 021 115 171A seals, omit the spacer rings, and I add-omit the deflector plate. Here's why:

Four scenarios:

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Scenario #1 has the deflector shield and the spacer rings:

Installing the oil cooler we see that the deflector plate is holding the oil cooler up off the seal. The thin top piece of the deflector plate that is above the flange is just slightly thicker than the spacer rings:

(Sorry for the out of focus picture, by the time I realized it was too late and I had moved on.)

Maybe there is a deflector shield that doesn't have the top section? I don't have, nor have seen one made that way; and a third style deflector plate isn't documented in any of the literature I have access to.

Well, that's not going to work.

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Scenario #2 has the spacer rings, but no deflector plate:

We see that the rings hold the oil cooler up off the seal:

This scenario isn't going to work.

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Scenario #3 has no spacer rings and no deflector plate:

However, there is a slight tilt to the cooler to seal interface with just a hint of gap:

That might work, but seems less than ideal.

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Scenario #4 has a standard thickness 6mm washer on the stud that passes through the nose of the oil cooler:

This results in a nice even compression of the seal:

The oil cooler is down tight against the flange:

The main bolts are stacked with a washer on top, a washer on the bottom, a spring washer on the bottom and a self locking nut (not one with plastic insert):

I have two coolers one original off my 73 and one off a 72. Both have the 10 mm case and cooler. I assume the plug from the carb is just for testing the cooler for leaks. I also noticed the seals you have are the ones used for this set up , the new ones you used I noticed a bit of rubber flash one the seals hole, The older ones didn't have this. . I imagine both the coolers I have have less fins , I never knew there was any difference. My 73 came with the pressure switch adapter with the copper seals yet it has a bit of an angle where the pressure sender threads in.

I did notice it does seem easy to damage the cooler where it sets on the case since each bolt hole has a bit of a built in washer for lack of a better word. You used a washer to level yours , smart.
I haven't had mine off since 97 when I rebuilt the engine and as you said the books are not very clear on what seal to use and in 97 I had no PC . I just used the thin red 10 mm seals and placed the spacers on top of the cooler bolts and I forgot to install the two long bolts from the bottom and already had the heads on.

Since mine is fuel injected I was going to replace them while I had the runners off yet didn't since I didn't want to deal with the fuel injected wire harness . With carbs it seems so much easier.

Great job on the write up and photo's this will help many who are dealing with a rebuild who are doing it them self or just dealing with the cooler and seals.

This issue.....this question of "spacer" or washer....between case and cooler...or on the outside under the nut.....has been rattling around for ages. It also not just a type 1/type 3 thing. It a type 4 thing too.

I have seen both type 3's and type 4's that came ...KNOWN to be un-disturbed from the factory with the spacer (and it IS a spacer) between oil cooler and case...and on the outside of the oil cooler....and both were correct and neither leaked.

Here is the same thread and discussion on type 4 engines. If you want to see my pictures and analysis...drop to the last page...where I think this link takes you.

Anyone who tells you ...authoritatively....that its ONLY correct...when installed one way...is full of sh*t.
Too many differences in coolers and cases. I believe the factory included these spacers in the install kit to be used as the cooler and case dimensions required upon assembly.

I didn't use the spacer washers on my 73 and the cooler was on the stock engine from 85 to 97 12 years and looked like this.

It's about 40 % compressed compared to a new seal of the same brand.

I still have it , it never split and is still to this day flexible. I used the same cooler on a 72 case and looking with a mirror and flashlight they look about the same. I didn't see any difference it the cases at all one the original was an X this one the 72 is a U.

I have no idea who made these yet even as old as they are and the unused ones are they are still flexible. I know I first set the seals in place these are the 10mm case and cooler and then placed the spaces then the cooler and could see it would never compress let alone seal.

I didn't use the spacer washers on my 73 and the cooler was on the stock engine from 85 to 97 12 years and looked like this.

It's about 40 % compressed compared to a new seal of the same brand.

I still have it , it never split and is still to this day flexible. I used the same cooler on a 72 case and looking with a mirror and flashlight they look about the same. I didn't see any difference it the cases at all one the original was an X this one the 72 is a U.

I have no idea who made these yet even as old as they are and the unused ones are they are still flexible. I know I first set the seals in place these are the 10mm case and cooler and then placed the spaces then the cooler and could see it would never compress let alone seal.

Yep....as I noted in the thread in that link I posted.....its about both the cooler dimensions and sometimes (at least on type 4) about the case dimensions as well. You can end up witn a cooler that needs the spacers between itself and the case....and it can need them on "virtually" every case you attache it to. It means the cooler isbuilt ib a specific way.

Then one day you put it on a case....and it cant seal the seals.....and needs the spacers taken out. Its probably the case thats different. Ray

I assume the plug from the carb is just for testing the cooler for leaks.

Yes, The plug is handy during clean-up, testing, and installation. (And thanks to Erik L. for putting me on to using that plug.)
When you are done:

Including using the correct non-tapered oil cooler switch with a sealing ring.
Every used oil cooler that came my way with a switch installed, had the (wrong) tapered-switch, which is only caught by two threads, or has been cranked down into the cooler to the point of fouling up the threads in the oil cooler boss.

blues90 wrote:

and I forgot to install the two long bolts from the bottom and already had the heads on.

Yes, interesting that the Type 3 parts book (with supplements) shows them installed with the bolts going down. The Haynes has a drawing showing them going up. From the factory----I don't know.

And one other note on cleaning up. You can get the product in this picture from your local HVAC store. The HVAC guys use it to clean the coils in your home air conditioner unit. (it says no rinse for the intended purpose, but for this purpose, ---Rinse!)

I wish vw used threaded studs like the T-4 engine used.I see no reason they used bolts and nuts. It could be done simply by installing threaded inserts in the two holes then fit double threaded rods in place.

About three months ago I had the runners off and now wish I had replaced the cooler seals . I can see because I wiped the top of the case off there is wet oil near the cooler seals mostly by the front most seal , it's not the cooler that leaks. The leak didn't look bad when I did the work because the oil was dry yet once I wiped the case top around the cooler down I can't see it new oil . I just didn't want to deal with fighting all that's needed to remove the left upper tin just to remove the cooler. Now I wish I had.